Respiratory protection devices are used in a wide variety of service applications to protect users from the effects of toxic or irritant particulate materials dispersed in the air. Such respirators are only fully effective, however, if they fit the user's face and head and if they have been donned properly. Performing a negative pressure fit check is a common method of ensuring proper facepiece fit and to ensure that the facepiece has been properly donned. This can typically be accomplished by using ones palms to cover the inlet of the filters installed on the respirator facepiece and inhaling. The inhaled breathe causes a negative pressure within the facepiece and allows the user to assess the seal and leak tightness of the facepiece by observing the pressure decay within the facepiece. When using ones palms to cover the inlet of the filters, however, the force required to effect a proper seal between the palms and the filter may be substantial and may cause the user to deflect the face seal of the respirator creating either false negative or false positive results. When using low profile particulate filters (often referred to as “pancake” filters) this fit check can become difficult if not impossible as there may be no way to completely cover the entire media surface due to its size/shape.
Some particulate filters employ a rigid frame around the outside such that the media is only exposed on the top. This allows for the effective use of palm sealing, but such filters are typically neither low profile nor flexible enough to interface with other personnel protective equipment the way a typical pancake filter can. Other filter styles employ semi flexible internal frame structures which allow for the desirable personnel protective equipment interfaces previously discussed. However, such styles do not allow the user to perform a negative pressure leak check as the user cannot cover the entire surface area of the filter media due to their size and shape.
It would be desirable to provide an improved “pancake” style particulate and/or nuisance filter that incorporates a negative pressure check mechanism that is easily and reliably actuated by a user.